I tested this no-nonsense thermometer and it's super fast and accurate

I always use one of the best meat thermometers whenever I'm cooking protein. It reassures me that the meat is cooked to the correct temperature and that no one will be served undercooked protein. I don't trust myself to rely on guesswork, especially when I'm cooking a larger joint, which may look well done from the outside, but the internal temperature is impossible to judge.

There is a plethora of meat thermometers on the market, from instant-read thermometers, like the Thermapen ONE, to leave-in meat thermometers, like the CHEF iQ Sense, Meater Pro XL, and the Corsori Smart Meat Thermometer, which I've all recently reviewed, along with the Ninja ProChef Wireless Thermometer that I'm currently testing.

I see the benefit of using an instant-read thermometer, and to tell you the truth, before testing a whole bunch of leave-in thermometers at Tom's Guide, I'd always rely on an instant-read thermometer for speed. So, I was more than happy to get the opportunity to test the Thermapen ONE in my home for a week. Here's how it went.

Thermapen ONE: Price and availability

Thermapen ONE: Design

The design of the Thermapen ONE is simple, which makes it easy to use, and because it’s not smart like the CHEF iQ Sense, there’s no need to download an app, pair devices, or set up cooking programs each time you want to use the thermometer. The Thermapen One is ready to use whenever you need it.

The probe tucks neatly into a groove within the main body of the device and is easy to store, ensuring the pointed end doesn’t get damaged or cause any harm. Then, once the probe is pulled out, it becomes active.

What’s more, it fits comfortably in the hand as being able to adjust the probe to different angles, makes placement of the probe incredibly flexible.

There is also a small light sensor on the front of the device, beside the display, that monitors when the light fades. When the light level reaches a certain point, the backlight comes on to illuminate the reading. You can test it by placing your thumb over the sensor and shielding the display with your other hand.

The casing is solid and comes in a range of bright color-popping colors directly from ThermoWorks. I tested the Red version, which is among other bright shades, such as Yellow, Green, Blue, Orange, Pink, and Purple. However, if you prefer a more subtle tone, it’s available in White, Black, and Charcoal.

How does the probe work?

The probe has a micro-thermocouple located at the probe’s tip, and to work, one eights of an inch of the probe must be immersed into the food. ThermoWorks explains that the thermocouple is a set of two heat-sensitive wires that produce a voltage related to temperature difference, and this technology is typically only found in professional-grade thermometers. The company also claims that this sets the Themapen ONE above its competitors.

Thermapen ONE: Ease of use

(Image credit: Tom's Guide / Camilla Sharman)

(Image credit: Tom's Guide / Camilla Sharman)

(Image credit: Tom's Guide / Camilla Sharman)

Overall, the Thermapen ONE is easy to use and, as mentioned above, is ready for action without any setup. As soon as you move the probe, the thermometer is activated, and you can immediately place it into whatever you want to measure. I also found that it has more all-round use in the kitchen than a leave-in meat thermometer, such as the CHEF iQ, which you couldn’t use to monitor the temperature of liquids.

Customizing the settings

The one downside I found with the Thermopen ONE is accessing the customization buttons is difficult. Rather than being on the outside of the device, you can only change the settings by removing the screwed-in panel in the back, which also houses the battery. If you tend to use recipes in Fahrenheit and Celsius without doing a conversion yourself, it’s a faff to change.

Apart from changing the temperature measurement, you can also alter the battery display resolution from whole numbers (1°) to tenths of a degree (0.1°); this is particularly helpful if you are heating foods to precise temperatures, such as liquids for candies that need to be spot on. Another feature you can adjust is the sleep and wake modes, from 10 to 180 seconds in 10-second intervals.

User guides

The thermometer comes with operating instructions and a comprehensive user guide to get you up and running. The user guide details quick tips, guidance on what the thermometer does and doesn’t do, tips on using the device, how to perform an ice bath or boiling water test to check accuracy, and cleaning and care instructions. They are certainly worth reading to ensure you get the most out of using the Thermapen ONE.

And, unlike when using a thermometer that connects to an app that guides you to the correct cooking temperature, the reverse of the user guide features Chef & USDA recommended temperatures. It's worth keeping the guide close to hand for the temperature references, if nothing else.

Thermapen ONE: The ice challenge

An ice bath test is the easiest way to test the accuracy of any thermometer, and I carry it out on all the thermometers I review. ThermoWorks is confident that Thermapen ONE will perform as expected, and it even explains how to carry out the ice bath test in the user guide.

ThermoWorks states that the final resting temperature should be between 31.5 and 32.5°F (or -0.3°C and 0.3°C). I swapped my thermometer to read in Celsius during the test, which gave a final reading of 0.1°C — well within the range.

Thermapen ONE: Performance

This thermometer comes with its own Certificate of Calibration. What does this mean? The Certificate verifies that your individual thermometer has been calibrated against a precision thermometer in a laboratory and found to be accurate at 32°F (ice point) and 212°F (boiling point). It’s been signed by the testing technician and includes the date of testing and the product serial number.

Receiving the certificate gave me reassurance that the thermometer is highly accurate.

Getting ready to cook

Unlike a leave-in meat thermometer, there’s no fiddling around placing a probe correctly before starting a cook. And although not all leave-in thermometers connect to an app, when they do, it takes a few minutes to get everything connected and set up before you start the cooking process.

However, with an instant-read thermometer, you have to keep your eye on the game and check in when you think the protein is close to cooked. You won’t get a reminder that you need to check your meat.

(Image credit: Tom;s Guide / Camilla Sharman)

(Image credit: Tom's Guide / Camilla Sharman)

Roasting a whole chicken
I placed a large chicken into my Corsori TurboBlaze air fryer and set it to cook on the air fry mode at 195°C, with the target temperature of 165°F (74°C). I took several readings during the cooking process to gauge the internal temperature of the thickest section of meat, the breast. The thermometer registered the temperature very quickly, and I was able to place the food back in the air fryer without much delay. I think it would have taken slightly longer to juggle taking the temperature within my standard oven, whereas using an air fryer, I pulled out the drawer without removing the chicken completely onto my countertop.

Rather than removing the chicken when the temperature had reached 165°F, I removed it approximately 10 minutes before to allow the meat to rest and reach its final temperature. However, you do have to be hands-on with this process.

Cooking a chicken breast
Cooking a piece of protein as small as a chicken breast is far easier than dealing with a bigger joint, as the cooking time is shorter, and it’s simple to find the thickest part of the meat to monitor. And again, just like the roast chicken, the target temperature was 165°F, with the final reading at 170°F. Although this is higher than the desired final temperature, it is still perfectly acceptable without drying the meat.

However, it does prove the difficulty of having to regularly monitor the temperature without a smart device doing the hard work for you.

Cooking sausages

I don't need any excuses to cook sausages, so I set my air fryer to 195°C and started the cook. And while testing the Thermapen ONE, I used the Ninja ProChef wireless thermometer alongside it. As before, the Thermapen ONE gave me a quick digital reading within one second.

Thermapen ONE: Cleaning

The Thermapen ONE is no different from any other food thermometer — every time the probe monitors meat that isn’t cooked, it must be cleaned to prevent exposure to harmful bacteria. ThermoWorks recommends using anti-microbial wipes or sprays when needed, although wiping with a paper towel dampened with hot, soapy water is sufficient for domestic use.

The body of the device is waterproof, although it cannot sustain any length of time in water and is not dishwasher safe. It can be cleaned in exactly the same way as the probe.

Thermopen ONE: Verdict

I enjoyed the ease of using the Thermapen ONE, without opening an app or making sure a connecting hub or my mobile was charged. It’s also highly accurate and super fast. I can see the benefit of using an instant-read thermometer, along with one that is wireless. It’s also easy to clean and store, and the guidance that comes with the product is helpful.

However, you could find that your protein looks like it’s been attacked if you are constantly monitoring it, unlike a leave-in probe, which will only create one discreet hole unless you need to reposition it during the cooking process.

But, where it particularly excels is in testing liquids. This hand-held thermometer is super easy to insert into a pan of syrup, caramel, or any candy-like treat where precision is vital. I can see that it will come in handy when testing the temperature of homemade jam. It can also monitor water temperature when you require a poach, simmer, slow or rolling boil. In this department it can do so much more than a leave-in thermometer.

One disadvantage is the price, as there are cheaper instant-read thermometers available. Although, what you pay out you get back in accuracy, which is the product's USP.

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